The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structures.
In the past, the semiconductor industry utilized various methods and structures to produce class-D amplifiers. The prior class-D amplifiers had various applications such as audio power amplifiers for cellular phones. In such applications, the class-D amplifier converted an analog signal to a digital signal and used the digital signal to switch a load with digital switches. One example of such a class-D amplifier was disclosed in U.S. Pat. No. 6,614,297 issued to Score et al on Sep. 2, 2003. One problem with these prior class-D amplifiers was electromagnetic interference (EMI). If the value of the audio input signal was zero or close to zero, small amounts of noise on the audio input signal resulted in high frequency noise radiating from the output of the class-D amplifier.
Some methods to reduce the EMI involved the use of digital logic elements in the digital logic portion of the class-D amplifier. One example of such digital logic is disclosed in U.S. Pat. No. 6,847,257 issued to Edwards et al on Jan. 25, 2005. The digital logic elements of these class-D amplifiers removed all noise above a certain frequency which resulted in removing even audio sounds. This resulted in periods of complete silence during portions of some audio signals. The periods of silence often made uses of the audio equipment, such as a cellular phone, think the equipment was not operating properly.
Accordingly, it is desirable to have a class-D amplifier that has reduced electromagnetic interference without removing audio signals.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.